The invention relates generally to a power system and a method of generating power.
More particularly, the invention relates to a power system and a power generation method in which an a-c voltage source supplies current for a d-c consumer.
A known power system has an a-c voltage source which supplies a d-c consumer with current. The output voltage of the a-c voltage source is rectified in a rectifier and smoothed in a smoothing circuit before being fed to the d-c consumer. The smoothing circuit contains a smoothing capacitor which has a relatively high capacitance in order to minimize waviness in the d-c input voltage transmitted to the d-c consumer. A high capacitance is also of advantage when the smoothing capacitor is to serve as a buffer, that is, when the smoothing capacitor is to constitute a temporary voltage source in the event of a brief failure of the a-c voltage source or in the event that the d-c consumer temporarily draws an excessive load. Due to its high capacitance, the smoothing capacitor will not discharge completely between consecutive half waves of the a-c voltage during normal operation.
The output current of the a-c voltage source, and hence the input current to the rectifier, flows only while the amplitude of the a-c voltage exceeds the residual voltage in the smoothing capacitor. Consequently, the period of current flow during each half cycle of the a-c output voltage is generally much shorter than the period of the half cycle. The period of current flow decreases as the capacitance of the smoothing capacitor increases.
The short period of current flow results in an unfavorably high ratio of the effective value to the mean or average value of the current flowing through the rectifier. For a given mean or average value of the current, the rectifier must therefore be designed for a much higher peak value of the current than would normally be the case for the particular mean or average value.